docs: def unitResponse(self, band):
          """Put a flat spectrum of 1 photlam through this band and integrate.
          This is used internally for :ref:`pysynphot-formula-effstim`
          calculations."""
          #sumfilt(wave,0,band)
          # SUMFILT = Sum [ FILT(I) * WAVE(I) ** NPOW * DWAVE(I) ]
          total = band.trapezoidIntegration(band.wave, band.throughput)
          return 1.0/total